1. Field of the Invention
The present invention relates to a system for searching for alternative routes for bypassing a failure occurring at a node or link in a network.
Along with the application of technology for ultra-high speed transmission in recent years, the range of a network which a failure affects has gradually become greater. In particular, while failures at nodes due to fires, earthquakes, and other disasters may occur infrequently, they tend to affect a greater number of channels compared with failures at links and therefore have become serious problems which can no longer be ignored.
Accordingly, a high speed system for searching for alternative routes, which is able to perform processing for restoration of service not only in the case of failures at single links, but also failures at multiple links, has become necessary.
2. Description of the Related Art
Conventional systems for searching for alternative routes have been designed for fast restoration of service in the case of failures at single links. Once a failure occurs, they flood restoration messages to the network. The paths receiving the restoration message the fastest are allocated as alternative routes. And they set the maximum bundles of channels able to be allocated through those paths. If the related failure is not restored as a whole by one search for alternative routes, the system tries the search again to set alternative routes for as many channels as possible.
In the above conventional systems for searching for alternative routes, however, there was the problem that the rate of restoration of service from the failures significantly declines when a failure occurs at a node or a failure occurs at multiple links.